The present invention relates to an information recording apparatus of an optical magnetic recording system for recording information on a recording medium based on both operations of light and magnetism, a recording head employed in this information recording apparatus, and a method of manufacturing this recording head.
In recent years, a recording medium and an information recording apparatus of an optical magnetic recording system have been widely distributed. In this optical magnetic recording system, a further high-density recording has been required, like in other information recording system.
In order to satisfy this requirement, focus has been placed on a magnetic field modulation system for modulating a magnetic field, in addition to an optical modulation system for modulating light.
FIG. 15 is a schematic diagram showing one conventional example of an optical magnetic recording system that employs both the optical modulation system and the magnetic field modulation system.
A recording medium 10 shown in the drawing is formed with a recording layer 12 for having information recorded on the surface of a light-transmissive substrate 11. A transparent protection layer 13 is formed on the surface of the recording layer 12 for protecting this recording layer.
A magnetic head 20 is disposed at a position close to the protection layer 12 (for example, with a gap of about 2 to 4 xcexcm from the surface of the protection layer 12). The protection layer 13 has a thickness of about 5 to 10 xcexcm. Therefore, the magnetic head 20 is disposed at a position of about 10 xcexcm to 100 xcexcm from the recording layer 12.
A magnetic coil 21 of this magnetic head 20 is input with a modulation signal S as shown in the drawing, and a modulation magnetic field is formed.
For carrying out a magnetic field modulation, it is necessary to dispose the magnetic head 20 at a position extremely close to the recording layer 12 like about 10 xcexcm as described above. Therefore, an objective lens 31 for guiding a laser beam 30 to the recording layer 12 is disposed at a substrate 11 side. The laser beam 30 is irradiated from the substrate 11 side to the recording layer 12. In this example, the laser beam 30 is also modulated in recording information on the recording medium 10. This is called a laser pulse light-emission magnetic field modulation recording, which further improves the density of the tracks. Information is recorded on the recording layer 12 based on both operations of the magnetic field generated by the magnetic head 20 and the heating generated by the irradiation of the laser beam 30.
In order to achieve a high-density recording on the recording medium, it is necessary to increase the NA of the objective lens 31 and to form an extremely small light spot on the recording layer 12.
FIG. 16 is a schematic diagram showing one conventional example of forming an extremely small light spot on the recording medium.
As the objective lens, there are disposed a condensation lens 32 that is similar to the objective lens 31 shown in FIG. 15, and a semi-spherical lens 33, for example, that is called a solid immersion lens (SIL). Based on the use of the SIL 33, a laser beam 30a leaked from the SIL 33 to a position extremely near the SIL 33 is used as a light for recording on the recording medium 10. With this arrangement, it is possible to realize a certain level of high NA. From the viewpoint of only the light spot, it is considered possible to achieve a certain level of high-density recording.
However, this SIL 33 has a short depth of focus like a few xcexcn to 100 nm or below. Therefore, when it is tried to apply the system shown in FIG. 15 to the magnetic field modulation system, it is necessary to dispose the objective lens and the magnetic coil including this SIL 33 at the same side of the recording medium. For this purpose, it is necessary to dispose a magnetic coil 34 on the bottom surface 33a of the SIL 33. Consequently, it becomes necessary to use a coil without a core for allowing the laser beam 30 to pass through. This has a problem that it is difficult to obtain a magnetic field that has strength necessary for the high-speed modulation.
In the light of the above situation, it is an object of the present invention to provide an information recording apparatus capable of realizing a high-density recording based on both operations of light and a magnetic field, a recording head that is suitable for use in this information recording apparatus, and a method of manufacturing this recording head.
In order to achieve the above object, according to the present invention, there is provided a recording head disposed between a light source and a recording medium. This recording head comprising: a magnetic head for generating a magnetic field toward the recording medium; and a light guide disposed on an optical path at the downstream of the magnetic head, for condensing an optical beam guided from the upstream of the magnetic head, and emitting this optical beam to the recording medium.
In the recording head of the present invention, it is preferable that the light guide comprising: a light guiding layer disposed on the optical path at the downstream of the magnetic head, for being incident with an optical beam guided from the upstream of the magnetic head; and a sharp-headed light guide disposed on the optical path at the downstream of the light guide, having a sharp head toward an aperture of the front end of the recording medium, for condensing an optical beam guided from the light guiding layer, and emitting the optical beam to the recording medium via the aperture.
In this case, it is preferable that the light guiding layer has a diffraction grating for guiding the optical beam to the optical-beam incident surface.
Further, according to the present invention, there is provided a recording head comprising: a light-transmissive substrate having a magnetic head made up of an embedded magnetic core, and a magnetic coil formed on an area surrounding the magnetic core on the surface facing the recording medium; a sharp-headed light guide with a sharp head toward the front end facing the recording medium, having a light-incident aperture for receiving an incidence of a light at a position with a predetermined distance from the front surface of the magnetic head that faces the recording medium, for condensing a light incident from the light-incident hole, and emitting the condensed light toward the recording medium from a light-emitting hole formed at the front end facing the recording medium; and a light guiding layer having the front surface facing the recording medium in contact with the light-incident hole, with the rear surface spread in contact with the front surface of the light-transmissive substrate, having an incident-light guide diffraction grating in the area in contact with the front surface of the light-transmissive substrate, and having a light-emission diffraction grating in the area in contact with the light-incident aperture, for introducing a light incident from the rear surface of the light-transmissive substrate via the incident-light guide diffraction grating, condensing the introduced light toward the light-incident hole, and emitting the condensed light toward the sharp-headed light guide via the light-emission diffraction grating.
The recording head has the above-described structure, and both the objective optical system and the magnetic coil are disposed at the same one side of the recording medium. Even when a light irradiated onto a portion of the magnetic head has been shielded by the magnetic head, only a small portion of the total optical beam is shielded. Therefore, it is possible to focus a light with sufficient intensity into an extremely small optical spot, and irradiate this focused beam onto the recording medium.
Moreover, based on the formation of the diffraction grating, it is possible to efficiently introduce the incident beam to the light guiding layer.
Further, according to the recording head of the present invention, it is possible to provide a magnetic head having a magnetic core. As compared with the conventional technique of providing a coil without a core, it is possible to increase the intensity of the magnetic field applied to the recording medium.
Further, according to the present invention, there is provided a method of manufacturing a recording head, the method comprising the steps of: forming an incident-light guide diffraction grating, and a groove for embedding a magnetic coil, on the surface of a light-transmissive substrate that is formed with a magnetic core embedding portion; embedding a magnetic core into the magnetic core embedding portion; forming a magnetic coil on the groove; forming a light guiding layer for introducing a light incident from the rear surface of the light-transmissive substrate to the front surface of the light-transmissive substrate after the magnetic coil has been formed, and condensing the introduced light at a light-condensing position facing the front surface of the magnetic coil; forming a diffraction grating for emitting a light condensed by the light guiding layer from the light guiding layer, at the light-condensing position facing the front surface of the magnetic coil on the surface of the light guiding layer; and forming a sharp-headed light guide having a sharp front end, for introducing a light condensed at the condensing position by the light guiding layer, and further condensing the light. It is possible to manufacture a recording head based on this manufacturing method, for example.
Further, according to the present invention, there is provided an information recording apparatus having a light source, and a recording head disposed between the light source and a recording medium, for recording information on the recording medium based on both operations of a heating on the recording medium by the light and magnetic force of a magnetic field, wherein the recording head comprising: a magnetic head for generating a magnetic field toward the recording medium; and a light guide disposed on an optical path at the downstream of the magnetic head, for condensing an optical beam guided from the upstream of the magnetic head, and emitting the condensed optical beam to the recording medium.
According to the information recording apparatus of the present invention, it is possible to carry out a high-density recording based on both operations of light and a magnetic field, regarding the magnetic head of the present invention as described above.
In the information recording apparatus of the present invention, the sharp-headed light guide has an aperture having a size of one half or below of the wavelength of a light emitted from the light source, as the light-emission aperture, for example.
Based on the forming of the extremely fine light-emission aperture in advance, it is possible to form an optical spot having an extremely small diameter on the recording medium, by irradiating a light leaked from this light-emission aperture onto the recording medium.
Moreover, in the information recording apparatus of the present invention, it is preferable to provide a slider mounted with the recording head and buoyant above the recording medium.
Based on the provision of a slider that has been conventionally used in the magnetic disk unit, for example, it is possible to dispose the recording head at a position extremely close to the recording medium for recording information.
Further, in the information recording apparatus of the present invention, it is preferable to provide a position control element for moving the recording head in parallel with the recording medium.
This positional control has also been carried out in the conventional optical disk unit to compensate for the eccentricity of the optical disk. It is also preferable to provide a mechanism for compensating for a relative positional deviation from the recording medium in the information recording apparatus of the present invention.
The information recording apparatus of the present invention also may be an apparatus for reading information recorded on the recording medium as well as recording information. This information recording apparatus may be structured such that the information recorded on the recording medium is read optically or magnetically, according to the characteristics and the like of the recording medium. For optically reading information, there is provided a reading head for optically picking up information recorded on the recording medium. For magnetically reading information recorded on the recording medium, there is provided a reading head for magnetically picking up information recorded on the recording medium.
As described above, according to the present invention, an optical magnetic recording system is employed, and it has become possible to carry out a high-density recording, and it has also become possible to further increase the recording capacity of the recording medium to a larger capacity. As a result, it is possible to reduce the cost of the recording medium per unit information volume.
In the present invention, as an optical near field is used, a short wavelength is not always necessary for the light source. When silicon is used at a light-transmission portion, for example, it becomes possible to use a semiconductor laser of 800 nm band.